1. Field of the Invention
The present invention relates to an articulated support stand with at least two arms which are pivotally interconnected through the intermediary of a lockable central joint which is traversed by a king pin, and which carry ball joints at their ends, which are commonly lockable with the central joint through the utilization of a clamping member and locking members, wherein the locking elements include push rods located interiorly of the arms which act on the ball joints, and which are actuatable through an opposite relative displacement of two components provided with inclined abutting surfaces.
Articulated support stands of that type are utilized, for instance, as retractors during surgery. The articulated support stand which is equipped with the central joint and the two ball joints can be fixed in every suitable position by means of a single manipulation.
2. Discussion of the Prior Art
From U.S. Pat. No. 3,240,516 there has previously become known an articulated support stand for that type. Seated on the king pin within the central joint of this stand are two conical sleeves which act on complimentary tapered surfaces at the ends of the push rods. Upon the actuation of a clamping lever with an eccentric, the sleeves are pulled towards each other and push rods pressed outwardly. Due to the internal friction the clamping forces which are to be applied are extremely high, and the central joint must be corresponding largely dimensioned. The wedging surface tend towards automatic locking and to seizing so they must be sufficiently lubricated which, however, renders sterilizing more difficult. The axial forces which occur during clamping have the tendency to tilt the push rods within the arm tubes.
A further articulated stand of this type of construction is described in German Published Patent Application 27 17 828. In this support stand, wedge-shaped clamping elements are forced apart through pressure rollers, whereupon the pressure is transmitted to the push rods. The central joint consists of a large number of individual components which render the manufacture more expensive and the assembling more difficult. This is particularly disadvantageous during sterilizing. In the event that the joint is not disassembled there is no protection for satisfactory sterilizing. In case that, contrastingly, it is disassembled, then the reassembly is connected with difficulties and with a large demand on time.